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Recently, we discussed the discovery of a black hole in a neighboring galaxy. It appears to be swallowing matter at a rate that's close to the theoretical limit on this process. This discovery raises the hope that we'll be able to get a clear view of the environment around the black hole, where the inflow of matter leads to the formation of particle jets that expel some of the matter at relativistic speeds. This process is also thought to power quasars, where the jets of supermassive black holes generates some of the brightest objects in the Universe.

But there's a small caveat that should temper astronomers' enthusiasm: we don't know for a fact the same process that powers jets from small black holes can scale up to objects that may weigh billions of times the mass of the Sun. Conveniently, in the same week this discovery was announced, another team of astronomers has provided evidence that all of these jets have similar properties.

Although black holes are happy to swallow most of the matter that comes their way, a bit of it escapes—if by "escapes" we mean "gets shot away from the black hole at nearly the speed of light." These jets of particles are so energetic that, in at least some cases, they're entirely thrown out of the galaxy where the black hole resides. Various models indicate the black hole's intense magnetic field lines power the jets by latching on to charged particles in the matter that is falling in towards the event horizon.

We've got some great models of how this can work and how the environment narrows and focuses the jets, sending them in a beam lined up with the black hole's north and south pole. But we're only just starting to resolve some of the features near the black holes at the center of quasars. Given that most quasars are quite distant and the core of galaxies are crowded places, there are likely to be limits to how well we can ever resolve the details of the environment that forms the jets.

That explains the appeal of objects like gamma ray bursts (which result from a black hole's formation) and microquasars (stellar-mass black holes actively swallowing matter). These have been found much closer to Earth (including in our own galaxy) and don't necessarily reside in the galactic center, which means we should be able to get a relatively unobstructed view of one. And, with a bit of luck, we could potentially get a clearer perspective on the jets' formation.

But that raises the question of whether what we learn from these smaller bodies is actually relevant to black holes. Remember, these are so big that, if you dropped one in place of the Sun, its edges would extend out past the most distant planets. Earlier studies had suggested that microquasars and the full-sized versions operate through a similar process. The new study now extends this to gamma-ray bursts.

The authors searched for any reports of observations of the jets of black holes, ranging in size from the gamma-ray bursts that accompany the formation of black holes up to the blazars that are generated by supermassive black holes in galactic cores. These objects create gamma ray emissions as charged particles are whipped around at the base of the jets as they form. They also used radio observations to track the total energy in the jets.

When the two values were plotted against each other, the resulting points all fell along a single line. This suggests there's a simple, linear relationship between the two: the more energy in the jets, the stronger the gamma rays they can produce. So perhaps, there is indeed a single mechanism for accelerating the particles into a jet, one that works across all masses of black holes. The apparent mass independence should help constrain the models we make of jet formation and will mean that any information we get from one object will tell us about the remaining ones.

31 Reader Comments

The size of a black hole is indeterminately small. The size of the Schwartzchild(*) radius of a black hole, is a function of its mass. If you plonked a super-massive black hole (many billions of solar masses) down at the sun, it's Schwartzchild Radius would extend past the inner planets.

The size of a black hole is indeterminately small. The size of the Schwartzchild(*) radius of a black hole, is a function of its mass. If you plonked a super-massive black hole (many billions of solar masses) down at the sun, it's Schwartzchild Radius would extend past the inner planets.

The size of a black hole is the size of it's Schwartzchild radius. We have no way of determining the distribution of the mass inside the black hole (since matter that "enters" the black hold becomes frozen in time in the spot where it entered the hole, some matter should be distributed throughout the whole hole, but how we don't know).

The size of a black hole is indeterminately small. The size of the Schwartzchild(*) radius of a black hole, is a function of its mass. If you plonked a super-massive black hole (many billions of solar masses) down at the sun, it's Schwartzchild Radius would extend past the inner planets.

The size of a black hole is the size of it's Schwartzchild radius. We have no way of determining the distribution of the mass inside the black hole (since matter that "enters" the black hold becomes frozen in time in the spot where it entered the hole, some matter should be distributed throughout the whole hole, but how we don't know).

Except that general relativity demands that all mass be concentrated at the singularity, and that basically anything inside the radius of the event horizon can be dismissed.

The funny thing about black holes is that physics has a nasty habit of falling apart when you get near that event horizon, never mind once you cross it. The beautiful thing about black holes is that one can dismiss unobservable information as if it can't be observed it cannot affect anything else. That is to say, the mass distribution can be arbitrary, as none of its potential effects can be observed or felt outside the event horizon (though I gather a black hole is generally treated as spherical, though a sphere of zero volume and infinite density; I did mention how physics has a nasty habit of falling apart near singularities, didn't I?)

You can find the relevant wikipedia articles about singularities at the following links.

Does the gravity that comes from the black hole come from the radius, the center, or is it impossible to tell?

The gravity comes from the matter that makes up the black hole. Most of it is contained somewhere inside the event horizon, and occupies one or more of a googleplex possible distributions. There's currently no way to measure this distribution from thousands of lightyears away (hell, we can only do it with the moon thanks to a pair of carefully built satellites we sent to orbit the thing)

Does the gravity that comes from the black hole come from the radius, the center, or is it impossible to tell?

The gravity comes from the matter that makes up the black hole. Most of it is contained somewhere inside the event horizon, and occupies one or more of a googleplex possible distributions. There's currently no way to measure this distribution from thousands of lightyears away (hell, we can only do it with the moon thanks to a pair of carefully built satellites we sent to orbit the thing)

And the current state of the theory demands that you will see no distribution at all inside the event horizon, but rather a single point source. The matter is either in or it's out, and if it's in, it's all part of the singularity, so from outside, distribution is entirely irrelevant and unmeasurable.

Does the gravity that comes from the black hole come from the radius, the center, or is it impossible to tell?

The gravity comes from the matter that makes up the black hole. Most of it is contained somewhere inside the event horizon, and occupies one or more of a googleplex possible distributions. There's currently no way to measure this distribution from thousands of lightyears away (hell, we can only do it with the moon thanks to a pair of carefully built satellites we sent to orbit the thing)

And the current state of the theory demands that you will see no distribution at all inside the event horizon, but rather a single point source. The matter is either in or it's out, and if it's in, it's all part of the singularity, so from outside, distribution is entirely irrelevant and unmeasurable.

You see it as a point source, but that doesn't mean it is actually a point source. The question of "can a region of actually infinite density" exist is a bit more complex than saying "well our math says it can." It's irrelevant for the behavior of the black hole, of course, since we can't determine any distribution (that would "leak" information, which is impossible according to current theory, hence why it must mathematically be a point source), but it does have some ramifications in physics.

That said, information exchange with a black hole is already a problem, since black holes can "evaporate" mass but not information (via Hawking radiation, although that is still theoretical), which would mean information could be destroyed when the black hole finally disappeared (see: http://en.wikipedia.org/wiki/Black_hole ... on_paradox).

Does the gravity that comes from the black hole come from the radius, the center, or is it impossible to tell?

The gravity comes from the matter that makes up the black hole. Most of it is contained somewhere inside the event horizon, and occupies one or more of a googleplex possible distributions. There's currently no way to measure this distribution from thousands of lightyears away (hell, we can only do it with the moon thanks to a pair of carefully built satellites we sent to orbit the thing)

And the current state of the theory demands that you will see no distribution at all inside the event horizon, but rather a single point source. The matter is either in or it's out, and if it's in, it's all part of the singularity, so from outside, distribution is entirely irrelevant and unmeasurable.

You see it as a point source, but that doesn't mean it is actually a point source. The question of "can a region of actually infinite density" exist is a bit more complex than saying "well our math says it can." It's irrelevant for the behavior of the black hole, of course, since we can't determine any distribution (that would "leak" information, which is impossible according to current theory, hence why it must mathematically be a point source), but it does have some ramifications in physics.

That said, information exchange with a black hole is already a problem, since black holes can "evaporate" mass but not information (via Hawking radiation, although that is still theoretical), which would mean information could be destroyed when the black hole finally disappeared (see: http://en.wikipedia.org/wiki/Black_hole ... on_paradox).

It only has ramifications WITHIN the event horizon, though, so it doesn't really have any that matter. It's almost like if the children's game "peekaboo" were real, and what you couldn't see ceased to exist. If no effects can be observed, then none of it matters. Only those characteristics that can be gleaned from what IS observable even exist, for the sake of reality. Hell, that's one of the ways various superstring theories handle what's below the planck length: not observable, no effects can propagate, so none of it matters (gross simplication, but you get the idea).

At the end of the day, the answer to the mass distribution question is simple: its at the point of the singularity and anything else is irrelevant.

Are the jets really coming out on an axis like that? Why doesn't hole spew material out in a spherical fashion like light from the sun?

Maybe there is a special relativity where ejected matter is leaving at a speed greater than c so that it doesn't get sucked back in again... Else how would we have any radiation escaping hole as it would seem that holes would just keep hoovering up new and old ejected material and keep growing.

And to the best of my understanding, there's no such thing as "gravitational field lines," given that mass warps space uniformly around it, relative to the distribution of that mass. In the case of a black hole (a zero-volume point of infinite density, generally treated as spherical), that would be uniform in all three physical dimensions.

robert.walter wrote:

Are the jets really coming out on an axis like that? Why doesn't hole spew material out in a spherical fashion like light from the sun?

Maybe there is a special relativity where ejected matter is leaving at a speed greater than c so that it doesn't get sucked back in again... Else how would we have any radiation escaping hole as it would seem that holes would just keep hoovering up new and old ejected material and keep growing.

No, there's no special anything that permits anything to travel at greater than C. As described, the emissions are from the event horizon, not from inside that radius.

As to the layout depicted and what you're asking about there, you'd have to read the paper. I don't have the math for it and my background doesn't go deep enough here to puzzle it out or explain it myself.

And video footage of jets from the SWIFT satelite here: http://www.nasa.gov/mission_pages/swift ... -hole.html (presumably false-colour footage; the video doesn't load here at work, but the preview image on google and the description make it sound like false-colour video from one of our space-based telescopes.)

"if by "escapes" we mean "gets shot away from the black hole at nearly the speed of light." These jets of particles are so energetic that, in at least some cases, they're entirely thrown out of the galaxy where the black hole resides"

Was wondering if we can use this as a sling shot mechanism to get out of the galaxy.

Black holes are terribly interesting phenomena: I read Isaac Asimov's The Collapsing Universe some 25 years ago, and I am still trying to develop a proper model in my imagination. It is my (very limited) understanding that black holes represent a kind of opposite counterpart to Big Bang matter condensation, making them proper "edges" of the hyperspace Universe. Perhaps there is no matter within these black holes, only the energy remnant of collapsed matter having returned to its primordial form. It's almost poetic, but is it true?

The article talks about super-massive black holes being larger than the diameter of the orbit of Neptune. Is that correct? I thought even the most massive black holes were concentrated into a point. I thought it was the Event Horizon that could extend so far away, and that the Event Horizon was simply a "point of no return" but not the black hole itself. Is that correct?

The article talks about super-massive black holes being larger than the diameter of the orbit of Neptune. Is that correct? I thought even the most massive black holes were concentrated into a point. I thought it was the Event Horizon that could extend so far away, and that the Event Horizon was simply a "point of no return" but not the black hole itself. Is that correct?

There's been some talk about this in the comments - it sounds like since anything beyond the event horizon isn't measurable, nothing beyond there really matters, and the matter could be distributed any number of ways - we just don't know. The event horizon is the practical boundary of a black hole.

I'm not sure why this question got thumbs down. I'd love to know the answer, as well. Do these jets shoot out in a single direction, or in all directions, or what?

If they shoot out in a single direction, does that move the black hole around via jet propulsion?

Sorry if these are dumb questions. I'm just trying to understand what's happening with these jets.

The precise reason why the jets are so tight and out the poles is unknown. It's a general phenomenon that occurs in regular stars as well as compact objects, but the emissions from black holes are most powerful because the black hole environment has the greatest ambient energy. The jets don't move the hole because they come out on both sides, not changing the net momentum.

I'm not sure why this question got thumbs down. I'd love to know the answer, as well. Do these jets shoot out in a single direction, or in all directions, or what?

If they shoot out in a single direction, does that move the black hole around via jet propulsion?

Sorry if these are dumb questions. I'm just trying to understand what's happening with these jets.

The precise reason why the jets are so tight and out the poles is unknown. It's a general phenomenon that occurs in regular stars as well as compact objects, but the emissions from black holes are most powerful because the black hole environment has the greatest ambient energy. The jets don't move the hole because they come out on both sides, not changing the net momentum.

Quick question: if these things are so powerful and in the center of most galaxies, what happens when they get to close to each other? I've been reading science articles about galaxies "hitting" each other (though most of the hit is just them passing through each other since they are so spread out over such a wide area), so how do the black holes react? What happens if a jet of that matter shooting out leaves the galaxy at 90 degrees to the plane of the galaxy were to hit another super massive black hole barreling in?

The size of a black hole is the size of it's Schwartzchild radius. We have no way of determining the distribution of the mass inside the black hole (since matter that "enters" the black hold becomes frozen in time in the spot where it entered the hole, some matter should be distributed throughout the whole hole, but how we don't know).

Yes, the BH size is it's Schwartzchild radius. No, the different observers tell different stories:

"To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.[47] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it.[48] At the same time, all processes on this object slow down, for a fixed outside observer, causing emitted light to appear redder and dimmer, an effect known as gravitational redshift.[49] Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.

On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time without noting any singular behaviour. In particular, he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.[50]"

"In black hole theory, the black hole membrane paradigm is a useful "toy model" method or "engineering approach" for visualising and calculating the effects predicted by quantum mechanics for the exterior physics of black holes, without using quantum-mechanical principles or calculations. It models a black hole as a thin classically-radiating surface (or membrane) at or vanishingly close to the black hole's event horizon. This approach to the theory of black holes was created by Kip S. Thorne, R. H. Price and D. A. Macdonald.

The results of the membrane paradigm are generally considered to be "safe"."

It is the membrane paradigm that transforms the Unruh effect, from sufficiently high gravity to affect an accelerated observer by immersing it in a thermal blackbody radiation. into so called Hawking radiation.

"It’s often said that it is difficult to reconcile quantum mechanics (quantum field theory) and general relativity. That is wrong. We have what is, for many purposes, a perfectly good effective field theory description of quantum gravity. It is governed by a Lagrangian ...

Nonetheless, at low energies, i.e., for ε ≡ E^2/Mpl^2 << 1, we have a controllable expansion in powers of ε. ...

In other words, as an effective field theory, gravity is no worse, nor better, than any other of the effective field theories we know and love.

The trouble is that all hell breaks loose for ε ~ 1." (Eg around black holes, when Unruh radiation starts to occur.)

sporkwitch wrote:

In the case of a black hole (a zero-volume point of infinite density, generally treated as spherical),

That isn't coherent ("point", "spherical"). See my previous comment on how we don't know yet beyond the collapse into the event horizon. The whole point [sic!] with string theory is that it can avoid a lot of singularities. Hopefully BH innards are one of those.

I've been reading science articles about galaxies "hitting" each other (though most of the hit is just them passing through each other since they are so spread out over such a wide area), so how do the black holes react?

"if by "escapes" we mean "gets shot away from the black hole at nearly the speed of light." These jets of particles are so energetic that, in at least some cases, they're entirely thrown out of the galaxy where the black hole resides"

Was wondering if we can use this as a sling shot mechanism to get out of the galaxy.

The gravitation forces are strong enough to tear molecules apart. The radiation would be strong enough to "dissolve" almost any material you can create.

Thank you for the clarifications and expansions. I would only like to clarify my own intent regarding my statements.

As to things going wonky when we get near a black hole, I mean the singularity. I recognize that the event horizon extends far beyond this, and that as long as observation is still possible (the event horizon hasn't been crossed) we still understand (as much as we ever can) how things work. It's once you cross the event horizon that things go crazy, but we can generally dismiss them for the reasons already mentioned.

As to referring to the zero-volume/infinite-density point, and it being treated as a sphere, I was referring to the same as you: for the purposes of the math, it's treated as a sphere (as is standard throughout point-particle physics); I do understand that a point cannot be a sphere, as a sphere is three-dimensional, a circle two-dimensional, and a point, by definition, is only one-dimensional.